Process of making colloidal lead



Nov. 9, 1937. D, M. PHILLIPPI ET AL PROCESS OF MAKING COLLOIDAL LEAD Hi MM! :11

INN! I W z v Hm AM 2 m m III w H mm 0% H l Old on W El Filed Aug. 16, 1955 NOV. 9, 1937. M, PHILLIPPI ET AL, 2,098,710

PROCESS OF MAKING COLLOIDAL LEAD Filed Aug. 16, 1935 2 Sheets-Sheet 2 Patented Nov. 1933?" hurrah stares meant,

PRGQESS @lF MAKING CQLLQHDAL LEAD Dale M. Phillippi and .llames IE. illlilson, Dayton, Ohio, assignors to General Motors iliklirpbration.. Detroit, Mich, a corporation of? Application August 16,

6 Claims.

This invention relates to the reduction of metals to a very finely divided condition, some portions of which are of colloidal dimensions. It particularly relates to a process and apparatus for producing colloidal suspensions of lead, lead alloys, or other metals and alloys, in water or other liquid media. This process and means are improvements in the field of electrical dispersion of substances (pioneered by Bredig and others). The suspensions produced by the apparatus are of such concentration as to allow their adaptation to commercial processes on a practical basis. In the manufacture of such articles as clutch facing's and brake lining the present composition is a combination of asbestos fibers and metal binder, the metal binder being in very finely divided condition when applied to the fibers and being thereafter reassembled by heat and pressure, as set forth in the application of H. D. Geyer et al., Ser. No. 5576 filed February 8, i935, and of which this application is a continuation in part. It is for these and analogous purposes that the colloidal or semi-colloidal lead is used.

It is therefore an object of our invention to down a substance such as metal into a very finely divided or colloidal state.

It is a further object to accomplish this breakdown out of contact with air and so prevent or limit oxidation. It is moreover essential and convenient to collect and retain the broken-down material in a medium favorable to its subsequent utilization in the processing of some product.

With the above and other objects in view which will be more evident as the specification progresses, the embodiments of our invention will be better understood by reference to the following specification and drawings, in which,

Fig. 1 shows a schematic diagram of a mechanical means and electrical connections for carrying out the invention.

Fig. 2 is a sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a sectional view on the line 3-3 of Fig. 1.

Fig. 4 is a diagram similar to Fig. 1 showing a modified form of our invention.

In operating we use commercially pure metal to which may be added, if desired, agents to slow up the oxidation, change form of crystalline structure of metal, lower the melting point, or give any special properties to the metal or metallic suspension which may be desired. In the production bf our lead suspensions we have added approximately lg of 1% of bismuth to the lead provide a method of and means for breakinglass, Serial No. 36,5692?) (Cl. Ella-l1) electrodes with an apparent advantage of slowing up the oxidation action. We have also gained other desired characteristics of the finished friction material and in other cases the lead suspension itself by the addition of small amounts of 5 tin, tellurium, arsenic, antimony, etc.

It has been found that the crystalline structure of the electrodes as controlled by the alloying ingredients, the rate of cooling from the molten state, the pouring temperature, subsequent heat treatment, and any other factors that influence the structure of the metals have a decided efifect on the characteristics of the suspension and the relative efiiciency of the apparatus as a dispersion means. The lead is melted and poured into a hollow non-conducting ceramic tube such as that shown at 2. in the accompanying drawings. It has been found by experience that for lead (containing small amounts of hismuth) the casting is in a more satisfactory condition for the break-down ii the mass is allowed to stand in a molten condition for as much as 6 hours and then cooled slowly in air. It should be noted that the level of the top of the casting is less than half way up the ceramic tube and the 25 reason for the tube extending above will be brought forth clearly as the specification progrosses. in casting, one end of a power lead t is cast into the base, as shown at t.

The tube 2 is then set in a large cylindrical vessel 8 the bottom of which is covered by a hard rubber sheet ill, the central part of the sheet being countersunk as at E2 to accommodate the lower end of the ceramic tube. The outer surface of the tube is surrounded by a .metallic jacket M which is clamped thereon to prevent breakage and a triangular spreader I6 is secured. to the top of the assembly and extends to the inside wall of the vessel at spaced points to prevent the tube from tipping over. The metal, lead 40 in this case, therefore acts as the lower electrode and is connected by the lead 3 to one side of a double pole switch 68. The vessel is then filled with distilled water up to the level shown by the dotted line and totally submerges the tube. 45

Suspended on one end of a vertical steel shaft 2B is a spherical ball 22 which acts as the upper electrode, this particular shape being merely illustratlve as a flat circular disk may be used or other forms. The upper portion of the steel rod 20 is supported in vertical position by a long, cylindrical sleeve is supported on any suitable supporting platform such as 26. The central portion of the rod is supported by the bearing means 28 which is composed of an outer shell, the

inner'surface of which is threaded and into which screws a bushing 3t. A setscrew 232 is threaded I which will be more clearly set forth at a later through the outer surface of the casing'and abuts I the bushing 39 to hold. it in any desired position. The purpose of theadjustable bushing, through which the rod slides, is to act'as a clutch trip,

point. Just above this trip is a two piece spring loaded clutch having two faces 34i bearing against each opposite side of the rod, these two halves being supported on a cross rodiliiwhich' is spring biased by spring 38 which. extends between one end of the cross bar and the frame.

adjustable eccentric 42 on the shaft 43 of the motor which is supported on the platform 26. Therefore','as the eccentric causes the bar it to,

'move up and down, the clutch member, which presses against the outersurfaceof the'rod 20,,

' causes it also to reciprocate and the setting of the bushing 30, which contactsone portion of the clutch, will vary the point at which the clutchis released; The stroke of the rod may be adjusted by adjusting the eccentric member 42 to cause reduce to small particles.

larger or smaller gaps between the upper copper electrode 22 andthe lowerleadelectrode.

bushing 3D,-allow's the'copper electrode to be fed down as the lead electrode is decomposed so that the stroke or distance between the two'atthe' up per end of the stroke is always thesame even though the level of the lead may change and sink downin the ceramic tube 2. I I

the number of arcs drawninay be tabulated.

Connected to thesteel rod above the copper electrode at point 50 is a cable 52, the other end of which is also connected to the switch IS in proximity to the cable 4.' From the opposite pole of the switch member, to which the cable 52 is attached, is a cable 54 connected to one side of a generator 58. The opposite pole of the switch member is connected by a cable 58 to a series of reactance units 60 which may be varied as the conditions require. The other side of the reactance units is connected by a cable 62 to the opposite pole of the generator 56. The generator is driven by a motor 64, which is run from any suitable A. C. supply 86. It should also be noted that the lead is connected to the negative side of the generator and the copper to the positive. The D. C. motor 44, which supplies the vertical reciprocation to the rod 20, is supplied from any suitable D. C. supply 68 having a suitable switch and a rheostat 12 in its circuit to give any desired speed changes for the process.

The salient features therefore of this apparatus are as follows: I

1. The utilization of a long, ceramic tube within which a quantity of lead is cast which is desired to This tube is placed in a vertical position and immersed in water. In this way the small particles which are disintegrated by the arc, and are not as yet of sufficiently small dimensions, cannot be discharged laterally but remain in the proximity of the electrode and must be forced out over the tube and therefore do not leave until they are of sufllciently small size. The use of'the water is to cool and condense the dispersed metal vapors formed by the heat of the Theslip action of the clutch, when it is released by the arc, and also to serve'as a medium inwhich the I I metal may remain until its finaldisposition in I some process or product. I I I I .2. The use of a Verticallyreciprocated upper electrode whose stroke may be maintained constant and which is automatically fed, down as the lower electrode disintegrates.

. 3. The use of a D. C. motor to drive the afore- I the generatorcircuit supplying the, electrodes for the arcto'varythe characteristics of this circuit to give a more satisfactory result. I

5. The use of theproper conditioning of the 7 lead electrodes .bycontrol of precasting conditions and pouring temperature, cooling rates, heat treatment followingcasting, and bythe addition 'of'smallamounts of the proper alloying ingredi-' I ents to the metalbeing dispersed so as to provide the most stable suspensionandthe greatest dissumed.

The ceramic tube 2 with its casing 14 is placed in an upright position in the vessel 8 and the it from over-turning. The vertical rod 20 is then placed in position with the electrode 22 within the integration rate per unit of electrical energy con I spreader l6; clamped on the upper end to preventupper portion of the ceramic tube'and contacting the upper surface of thecast metal. The D. C.

speed regulated to the desired point by the rheo stat it. The bushingtilis then turned toa, position to which the clutchmember 34 makes slight contact therewith so that the clutch will be re.-

motorM is started by closing switch 10 and the leased to allow the upper electrode to, feed ,down- I wardly. Thebushing til-is then set in place by p I set screw 32. The length of the stroke of therod 26) is adjustable on the eccentric member @2 and y of course this is set before the motor is started. After the motor 44 has been placed in operation and all the apparatus adjusted, the switch 88 is closed which connects the negative side of the generator 56 to the lower or lead electrode and the positive side thereof to the copper electrode. Then as the copper electrode tends to move from the lead, an arc will be drawnwhich will disintegrate the upper surface of the lead electrode and reduce the metal. It should be mentioned that the wear on the copper electrode is negligible. The particles of lead are kept near the are by the tube until they are of sufliciently small size. These small particles gradually flow out of the upper There are many variables in the system, for

example: the voltage of the generator, the current, the current density at the electrode contacts, the contacts per minute between the two electrodes, the length of the stroke of the movable electrode, which influences the length of the arc, the nature of the contact between the two electrodes, the elapsed time of the run resulting in greater or lesser concentration of the suspension, size, mass, material and preparation of the opposing electrodes, the temperature of the water and the amount of reactance placed in the circuit.

By suitably varying any one orall of these elements, we may obtain different desired results current.

aosario depending upon the particular set-up. It has been found essentiaLior example, to have incorporated acertain amount of reactance in the circuit, and to change the amount of this reactance to suit various combinations of other factors. Thus, in the following tabulation, it will be seen that more reactance is required when the dispersable electrode is made of lead plus /2% of bismuth which givesan optimum of 7.4 ohms than when it is made of lead plus 1% of tin which has a 2.4 ohm optimum. The table serves also to give an indication of the amount of reactance necessary when working with dispersable electrodes of 3" diameter, current of 140 to 150 amperes, and 600 contacts per minute over the period of one hour. It shows, moreover, in the case of lead plus bismuth, how the yield may be increased by lengthening the stroke, up to the point where increased power requirements out of proportion with the higher yields, or other deleterious effects, make further increase inadvisable. The costs given in this table are based upon the arbitrary figure of one cent per kilowatt-hour for electrical energy, 60 cycle A. C. It is evident that these costs include any losses in conversion to direct In these runs all the factors were maintained substantially constant with the exception of the stroke and inductive reactance:

hollow bushing are threaded into a-supporting bearing tilt]. Connected to the shaft 98 by any suitable bolt clamping means MES is a cable 988 the opposite end of which is connected to one terminal of a solenoid coil M9, the opposite side of the solenoid coil being connected by wire M2 to the other side of the double pole switch 92 and thus to the D. 0. power supply.

Pivotally connected at i it to a vertical portion of the frame work bit is a horizontal arm Mil, one end of which is connected to a vertical link M8 the lower end of which is connected to a clutch mechanism 826 which is identical with the clutch members 3d, 36 and 33, shown in the first modification of this invention. The opposite-end of the arm M6 is pivotally connected to a vertical rod iii which extends downwardly through the solenoid lit and has rigidly clamped to the lower extremity thereof an adjustable stop i2 3.

' The operation of this modification is as follows:

The copper or movable electrode is spaced above the lower lead electrode 86 and out of contact with the same and the switch 92 is then closed. Since the circuit is broken between the two electrodes the solenoid Md will exert no effect upon the vertical rod 822 and therefore will allow the rod $8 to be pulled down by gravity until the I Inductive reactance Length stmle ohms 1.2 ohms 2.4 ohms 4.9 ohms 7.4 ohms 10.0 ohms Matl-Cost/lb. Mat'l-Costllb. Mat'l-Costllb. Mat'l-Cost/lb. Met'l-Gost/lb. Matl-Gost/lb.

For lead plus bismuth 3g" gms.6.& 525 gms.-5.4 525 gms.6.0 510 gms.6.0$ 54" 710 gum-5.151. 840 gms.4 44% 940 gms.3.9,t 950 gala-4.2a cg" 900 gms.4 0c 1180 gms.3.5; 970 gms.-3.8

For lend plus 1% tin 611 gms.-4.4 710 gms.4.75

- is 127 gms.l4.6 202 gms.8.8 709 gms.3.8 I

This definitely shows that as the stroke is in-' creased, all other factors remaining constant, that the amount of reactance necessary to give the most satisfactory results increases and that for different combinations or alloys that the optimum reactance will vary.

The temperature of the water medium surrounding the electrodes becomes quite high and. therefore the runs should not be too long either from this point of view or from the point of view that the suspension becomes too concentrated after a certain length of time run.

In Fig. i. is illustrated a modified form of apparatus for accomplishing the same result. In this form any type of suitable frame work tit is supplied upon one portion of which a vertical cylinder t2 is positioned which may be filled with water up to the level shown in the drawings. Within the cylinder 82 is placed a second smaller cylinder 86 which may be made of any electrical conducting medium such as steel. Cast in the lower portion of the cylinder M is a block of lead 85 which may include small amounts of tin, bismuth or other similar material as formerly explained in the specification. 'Connected to the upper rim of the cylinder 86 at 88 is one end of a power cable 80, the opposite end being connected to the double pole switch 92 which is connected to the D. 0. power supply 96. Supported above the two concentric cylinders t2 and 86 is a copper electrode 96 on a long steel shaft 98 in a manner similar to that shown in the foregoing specification, the upper end of the rod being supported in a vertical sleeve Ito and the center portion of the rod extending through a contacts 86 and 96 meet which will complete the electrical circuit through the solenoid and thetwo contacts. This will cause a comparatively large current to flow through the solenoid HG which will pull down upon the rod I22 and through the various links and levers cause an upward pull upon the copper electrode Q6 pulling it away from the lead electrode 36 and causing an arc therebetween. This action will continue until the arc has been drawn out to such an extent that it will collapse thereby breaking the circuit through the solenoid which will again allow the copper electrode to descend under gravitational action until contact was again made. This operation will continue indefinitely and of course, due to the arc, the lower contact will disintegrate giving a suspension as set forth in former parts of the specification. The clutch operation will be identical with that set forth in the former species of the invention so that it is not thought necessary to further describe that action as to how the copper electrode will automatically feeddownwardly as the lead electrode is disintegrated and eaten away. The stop me, on the lower end of the rod I22, may be adjusted to a position to give proper operation and not allow the copper electrode to be moved through to too great a distance. It is thus evident that in this type it is necessary to start the operation by hand in raising the copper electrode before the switch is closed and then allowing it to descend to make the first contact.

To point out the utilization of the solution obtained, a certain quantity of asbestos fibers are in a V! and this liquid, with the metal &

suspension, is poured into the vessel. The lead particles coat the outer surface of each of the fibers of the asbestos material andthe water is gradually drained ofi. This coating is probably due to several actions, first, each one of these small particles of lead carries a positive electrical charge as has been demonstrated by electro-phoretical experiments. In this respect the lead suspension is analogous to true colloidal particles. It is generally true that asbestos carries a negative charge respective to water (see Bancroft, Applied Colloid Chemistry page 259, lines 3 to '7) and therefore the lead particles possibly are attracted thereto. There is also the filtering action of a substance like asbestos which moves through a medium in a consolidated mass, tending to sweep it clean of suspended material. However the two above mentioned influences are not thorough in their action and we prefer to supplement them by the introduction of a coagulant such as carbon dioxide (C02). The action of this coagulant is to provide negative ions which will discharge the positive electrical charge carried by the dispersed lead particles. The resultant mass is freed of excess water, preformed to shape, molded under high pressure, and suitable temperature, and this converted into a friction material such as brake lining.

We claim:

1. In a process for making a colloidal suspension of metal, casting the metal in a member to only partially fill the same, immersing the whole in water, drawing an are from one surface of the metal intermittently and using reactance to smooth out the arc.

2. In a process for making a suspension of metal, casting metal in a ceramic member to partially fill the same, immersing the whole in water, drawing an are from one surface of the metal intermittently and utilizing reactance to smooth out the arc.

3. In a process for making a colloidal suspension of lead, casting lead to partially fill a ceramic tube, immersing the whole in water, supporting a reciprocable electrode in proximity to the lead for relative motion thereto, connecting the lead and the electrode to the output circuit of a generator and introducing into this circuit reactance to smooth out the arc.

4. In a process for making a colloidal suspension of lead, placing a portion of lead in liquid, bringing into proximity thereto an electrode at regular timed intervals, applying current to the lead and the electrode to cause an arc therebetween to disintegrate the lead and inserting reactance in the supply circuit to control the arc.

5. In a process for making a colloidal suspension of metal, casting the metal within a long tubular member to only partially fill the same, applying an are within the extension adjacent one face of the metal, the extension preventing particles of the metal from escaping until they have reached a sufficiently small size.

6. In a process for making a colloidal suspension of metal, melting metal and keeping the metal in the molten state for a substantial length of time, pouring the molten metal into a long tubular member to partially fill the same, allowing the metal to then cool slowly, placing the tube and cast metal under water, applying an electrode within the hollow portion of the tube, and supplying current to cause an arc between the metal and the electrode within the tube under water whereby the metal will be disintegrated but the tube will keep the particles adjacent the arc until they have reached a sufflciently small dimension.

DALE M. PHILLIPPI.

JAMES E. WILSON. 

